Multijunction Solar Cell Grading Layers for Radiation Hardness
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Solution Overview
Problem
Existing multijunction solar cells face challenges in achieving optimal efficiency and radiation hardness, particularly in space applications, due to complex design parameters and sensitivity to minority carrier diffusion length degradation from radiation exposure.
Innovation Solution
The design approach involves a multijunction solar cell structure with thinner base layers, specific doping levels, and band gap arrangements, including a p-on-n configuration with metamorphic layers, to enhance radiation hardness and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multijunction solar cell designs are used, then radiation hardness is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by modifying the base layer thickness to a specific range (0.5-2.0 micrometers) and adjusting doping concentrations (1E16-1E18 atoms/cm³) to achieve optimal radiation hardness while simplifying the design space. This resolves the contradiction by identifying specific parameter ranges that maintain reliability without requiring complex design iterations.
Solution Approach 2:
The patent implements local quality by creating a heterostructure with different material compositions (AlInGaP, GaInP, InGaP) in specific layers, each optimized for its local function. The base layer uses specific bandgap materials tailored for radiation resistance, while emitter layers are optimized for charge collection, resolving the complexity-reliability tradeoff through localized material optimization.
2Productivity
If base layer thickness is increased to improve optical absorption, then efficiency is improved, but weight and cost increase
Solution Approach 1:
The patent changes the base layer thickness parameter to an optimized range (0.5-2.0 micrometers) that balances optical absorption with weight reduction. This specific parameter range maintains sufficient photon absorption for high efficiency while minimizing material usage and weight, directly resolving the contradiction between productivity and weight.
Solution Approach 2:
The patent uses composite semiconductor materials (AlInGaP, GaInP, InGaP) with different bandgaps and densities to achieve high optical absorption in a thin base layer. These composite structures provide enhanced light absorption coefficients that allow reduced thickness while maintaining efficiency, thus reducing weight without sacrificing productivity.
3Productivity
If doping concentration is increased to improve carrier collection, then efficiency is improved, but radiation sensitivity increases
Solution Approach 1:
The patent optimizes the doping concentration parameter within a specific range (1E16-1E18 atoms/cm³) to achieve the right balance between carrier collection and radiation resistance. This parameter optimization ensures sufficient free carriers for efficient collection while avoiding excessive doping that would create more radiation-sensitive defect sites, resolving the efficiency-reliability contradiction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in improved efficiency, reduced weight, and lower costs for solar cell arrays, while maintaining or enhancing radiation resistance, thus addressing the limitations of current technologies.
Implementation Method 1
the ability to achieve spectral splitting of the incident radiation through the use of a plurality of photovoltaic regions with different band gap energies
Implementation Method 2
including a dopant grade in the base of the cell that creates an electric field to direct minority carriers to the junction of the device
Data Source
AI summary
A method of fabricating multijunction solar cell including an upper solar subcell and having an emitter of p conductivity type with a first band gap, and a base of n conductivity type with a second band gap greater than the first band gap; a lower solar subcell disposed below the upper solar subcell having an emitter of p conductivity type with a third band gap, and a base of n conductivity type with a fourth band gap greater than the third band gap; and an intermediate grading interlayer disposed between the upper and lower solar subcells and having a graded lattice constant that matches the upper first subcell on a first side and the second solar subcell on the second side opposite the first side, and having a fifth band gap that is greater than the second band gap of the upper solar subcell.